package org.csource.common;

import java.io.IOException;

/**
 * Freeware from:
 * Roedy Green
 * Canadian Mind Products
 * #327 - 964 Heywood Avenue
 * Victoria, BC Canada V8V 2Y5
 * tel:(250) 361-9093
 * mailto:roedy@mindprod.com
 */

/**
 * Encode arbitrary binary into printable ASCII using BASE64 encoding.
 * very loosely based on the Base64 Reader by
 * Dr. Mark Thornton
 * Optrak Distribution Software Ltd.
 * http://www.optrak.co.uk
 * and Kevin Kelley's  http://www.ruralnet.net/~kelley/java/Base64.java
 * <p>
 * Base64 is a way of encoding 8-bit characters using only ASCII printable
 * characters similar to UUENCODE.  UUENCODE includes a filename where BASE64 does not.
 * The spec is described in RFC 2045.  Base64 is a scheme where
 * 3 bytes are concatenated, then split to form 4 groups of 6-bits each; and
 * each 6-bits gets translated to an encoded printable ASCII character, via a
 * table lookup.  An encoded string is therefore longer than the original by
 * about 1/3.  The "=" character is used to pad the end.  Base64 is used,
 * among other things, to encode the user:password string in an
 * Authorization: header for HTTP.  Don't confuse Base64 with
 * x-www-form-urlencoded which is handled by
 * Java.net.URLEncoder.encode/decode
 * If you don't like this code, there is another implementation at http://www.ruffboy.com/download.htm
 * Sun has an undocumented method called sun.misc.Base64Encoder.encode.
 * You could use hex, simpler to code, but not as compact.
 * <p>
 * If you wanted to encode a giant file, you could do it in large chunks that
 * are even multiples of 3 bytes, except for the last chunk, and append the outputs.
 * <p>
 * To encode a string, rather than binary data java.net.URLEncoder may be better. See
 * printable characters in the Java glossary for a discussion of the differences.
 * <p>
 * version 1.4 2002 February 15  -- correct bugs with uneven line lengths,
 * allow you to configure line separator.
 * now need Base64 object and instance methods.
 * new mailing address.
 * version 1.3 2000 September 12 -- fix problems with estimating output length in encode
 * version 1.2 2000 September 09 -- now handles decode as well.
 * version 1.1 1999 December 04 -- more symmetrical encoding algorithm.
 * more accurate StringBuffer allocation size.
 * version 1.0 1999 December 03 -- posted in comp.lang.java.programmer.
 * Futures Streams or files.
 */

public class Base64 {

    /**
     * how we separate lines, e.g. \n, \r\n, \r etc.
     */
    private String lineSeparator = System.getProperty("line.separator");

    /**
     * max chars per line, excluding lineSeparator.  A multiple of 4.
     */
    private int lineLength = 72;

    private char[] valueToChar = new char[64];

    /**
     * binary value encoded by a given letter of the alphabet 0..63
     */
    private int[] charToValue = new int[256];

    private int[] charToPad = new int[4];

    /* constructor */
    public Base64() {
        this.init('+', '/', '=');
    }

    /* constructor */
    public Base64(char chPlus, char chSplash, char chPad, int lineLength) {
        this.init(chPlus, chSplash, chPad);
        this.lineLength = lineLength;
    }

    public Base64(int lineLength) {
        this.lineLength = lineLength;
    }

    /* initialise defaultValueToChar and defaultCharToValue tables */
    private void init(char chPlus, char chSplash, char chPad) {
        int index = 0;
        // build translate this.valueToChar table only once.
        // 0..25 -> 'A'..'Z'
        for (int i = 'A'; i <= 'Z'; i++) {
            this.valueToChar[index++] = (char) i;
        }

        // 26..51 -> 'a'..'z'
        for (int i = 'a'; i <= 'z'; i++) {
            this.valueToChar[index++] = (char) i;
        }

        // 52..61 -> '0'..'9'
        for (int i = '0'; i <= '9'; i++) {
            this.valueToChar[index++] = (char) i;
        }

        this.valueToChar[index++] = chPlus;
        this.valueToChar[index++] = chSplash;

        // build translate defaultCharToValue table only once.
        for (int i = 0; i < 256; i++) {
            this.charToValue[i] = IGNORE;  // default is to ignore
        }

        for (int i = 0; i < 64; i++) {
            this.charToValue[this.valueToChar[i]] = i;
        }

        this.charToValue[chPad] = PAD;
        java.util.Arrays.fill(this.charToPad, chPad);
    }

    /**
     * Encode an arbitrary array of bytes as Base64 printable ASCII.
     * It will be broken into lines of 72 chars each.  The last line is not
     * terminated with a line separator.
     * The output will always have an even multiple of data characters,
     * exclusive of \n.  It is padded out with =.
     */
    public String encode(byte[] b) throws IOException {
        // Each group or partial group of 3 bytes becomes four chars
        // covered quotient
        int outputLength = ((b.length + 2) / 3) * 4;

        // account for trailing newlines, on all but the very last line
        if (lineLength != 0) {
            int lines = (outputLength + lineLength - 1) / lineLength - 1;
            if (lines > 0) {
                outputLength += lines * lineSeparator.length();
            }
        }

        // must be local for recursion to work.
        StringBuffer sb = new StringBuffer(outputLength);

        // must be local for recursion to work.
        int linePos = 0;

        // first deal with even multiples of 3 bytes.
        int len = (b.length / 3) * 3;
        int leftover = b.length - len;
        for (int i = 0; i < len; i += 3) {
            // Start a new line if next 4 chars won't fit on the current line
            // We can't encapsulete the following code since the variable need to
            // be local to this incarnation of encode.
            linePos += 4;
            if (linePos > lineLength) {
                if (lineLength != 0) {
                    sb.append(lineSeparator);
                }
                linePos = 4;
            }

            // get next three bytes in unsigned form lined up,
            // in big-endian order
            int combined = b[i + 0] & 0xff;
            combined <<= 8;
            combined |= b[i + 1] & 0xff;
            combined <<= 8;
            combined |= b[i + 2] & 0xff;

            // break those 24 bits into a 4 groups of 6 bits,
            // working LSB to MSB.
            int c3 = combined & 0x3f;
            combined >>>= 6;
            int c2 = combined & 0x3f;
            combined >>>= 6;
            int c1 = combined & 0x3f;
            combined >>>= 6;
            int c0 = combined & 0x3f;

            // Translate into the equivalent alpha character
            // emitting them in big-endian order.
            sb.append(valueToChar[c0]);
            sb.append(valueToChar[c1]);
            sb.append(valueToChar[c2]);
            sb.append(valueToChar[c3]);
        }

        // deal with leftover bytes
        switch (leftover) {
            case 0:
            default:
                // nothing to do
                break;

            case 1:
                // One leftover byte generates xx==
                // Start a new line if next 4 chars won't fit on the current line
                linePos += 4;
                if (linePos > lineLength) {

                    if (lineLength != 0) {
                        sb.append(lineSeparator);
                    }
                    linePos = 4;
                }

                // Handle this recursively with a faked complete triple.
                // Throw away last two chars and replace with ==
                sb.append(encode(new byte[]{b[len], 0, 0}
                ).substring(0, 2));
                sb.append("==");
                break;

            case 2:
                // Two leftover bytes generates xxx=
                // Start a new line if next 4 chars won't fit on the current line
                linePos += 4;
                if (linePos > lineLength) {
                    if (lineLength != 0) {
                        sb.append(lineSeparator);
                    }
                    linePos = 4;
                }
                // Handle this recursively with a faked complete triple.
                // Throw away last char and replace with =
                sb.append(encode(new byte[]{b[len], b[len + 1], 0}
                ).substring(0, 3));
                sb.append("=");
                break;

        } // end switch;

        if (outputLength != sb.length()) {
            System.out.println("oops: minor program flaw: output length mis-estimated");
            System.out.println("estimate:" + outputLength);
            System.out.println("actual:" + sb.length());
        }
        return sb.toString();
    }// end encode

    /**
     * decode a well-formed complete Base64 string back into an array of bytes.
     * It must have an even multiple of 4 data characters (not counting \n),
     * padded out with = as needed.
     */
    public byte[] decodeAuto(String s) {
        int nRemain = s.length() % 4;
        if (nRemain == 0) {
            return this.decode(s);
        } else {
            return this.decode(s + new String(this.charToPad, 0, 4 - nRemain));
        }
    }

    /**
     * decode a well-formed complete Base64 string back into an array of bytes.
     * It must have an even multiple of 4 data characters (not counting \n),
     * padded out with = as needed.
     */
    public byte[] decode(String s) {

        // estimate worst case size of output array, no embedded newlines.
        byte[] b = new byte[(s.length() / 4) * 3];

        // tracks where we are in a cycle of 4 input chars.
        int cycle = 0;

        // where we combine 4 groups of 6 bits and take apart as 3 groups of 8.
        int combined = 0;

        // how many bytes we have prepared.
        int j = 0;
        // will be an even multiple of 4 chars, plus some embedded \n
        int len = s.length();
        int dummies = 0;
        for (int i = 0; i < len; i++) {

            int c = s.charAt(i);
            int value = (c <= 255) ? charToValue[c] : IGNORE;
            // there are two magic values PAD (=) and IGNORE.
            switch (value) {
                case IGNORE:
                    // e.g. \n, just ignore it.
                    break;

                case PAD:
                    value = 0;
                    dummies++;
                    // fallthrough
                default:
               /* regular value character */
                    switch (cycle) {
                        case 0:
                            combined = value;
                            cycle = 1;
                            break;

                        case 1:
                            combined <<= 6;
                            combined |= value;
                            cycle = 2;
                            break;

                        case 2:
                            combined <<= 6;
                            combined |= value;
                            cycle = 3;
                            break;

                        case 3:
                            combined <<= 6;
                            combined |= value;
                            // we have just completed a cycle of 4 chars.
                            // the four 6-bit values are in combined in big-endian order
                            // peel them off 8 bits at a time working lsb to msb
                            // to get our original 3 8-bit bytes back

                            b[j + 2] = (byte) combined;
                            combined >>>= 8;
                            b[j + 1] = (byte) combined;
                            combined >>>= 8;
                            b[j] = (byte) combined;
                            j += 3;
                            cycle = 0;
                            break;
                    }
                    break;
            }
        } // end for
        if (cycle != 0) {
            throw new ArrayIndexOutOfBoundsException("Input to decode not an even multiple of 4 characters; pad with =.");
        }
        j -= dummies;
        if (b.length != j) {
            byte[] b2 = new byte[j];
            System.arraycopy(b, 0, b2, 0, j);
            b = b2;
        }
        return b;

    }// end decode

    /**
     * determines how long the lines are that are generated by encode.
     * Ignored by decode.
     *
     * @param length 0 means no newlines inserted. Must be a multiple of 4.
     */
    public void setLineLength(int length) {
        this.lineLength = (length / 4) * 4;
    }

    /**
     * How lines are separated.
     * Ignored by decode.
     *
     * @param lineSeparator may be "" but not null.
     *                      Usually contains only a combination of chars \n and \r.
     *                      Could be any chars not in set A-Z a-z 0-9 + /.
     */
    public void setLineSeparator(String lineSeparator) {
        this.lineSeparator = lineSeparator;
    }

    /**
     * Marker value for chars we just ignore, e.g. \n \r high ascii
     */
    static final int IGNORE = -1;

    /**
     * Marker for = trailing pad
     */
    static final int PAD = -2;

    /**
     * used to disable test driver
     */
    private static final boolean debug = true;

    /**
     * debug display array
     */
    public static void show(byte[] b) {
        int count = 0;


        for (int i = 0; i < b.length; i++) {
            if (count == 8) {
                System.out.print("  ");
            } else if (count == 16) {
                System.out.println("");
                count = 0;
                continue;
            }
            System.out.print(Integer.toHexString(b[i] & 0xFF).toUpperCase() + " ");
            count++;

        }
        System.out.println();
    }

    /**
     * debug display array
     */
    public static void display(byte[] b) {
        for (int i = 0; i < b.length; i++) {
            System.out.print((char) b[i]);
        }
        System.out.println();
    }

    /**
     * test driver
     */
    public static void main(String[] args) {
        test();
        System.exit(1);

        if (debug) {
            try {
                Base64 b64 = new Base64();
                String str = "agfrtu��etʲ1234�ٴ�erty��234����2344ʲ��";
                String str64 = "";

                //encode
                str64 = b64.encode(str.getBytes());
                System.out.println(str64);

                //decode
                byte[] theBytes = b64.decode(str64);
                show(theBytes);
                String rst = new String(theBytes);
                System.out.println(rst);
                System.out.println(str);
            } catch (Exception e) {
                e.printStackTrace();
            }
            //getBytes(String charsetName);
/*
         byte[] a = { (byte)0xfc, (byte)0x0f, (byte)0xc0};
         byte[] b = { (byte)0x03, (byte)0xf0, (byte)0x3f};
         byte[] c = { (byte)0x00, (byte)0x00, (byte)0x00};
         byte[] d = { (byte)0xff, (byte)0xff, (byte)0xff};
         byte[] e = { (byte)0xfc, (byte)0x0f, (byte)0xc0, (byte)1};
         byte[] f = { (byte)0xfc, (byte)0x0f, (byte)0xc0, (byte)1, (byte)2};
         byte[] g = { (byte)0xfc, (byte)0x0f, (byte)0xc0, (byte)1, (byte)2, (byte)3};
         byte[] h = "AAAAAAAAAAB".getBytes();



         show(a);
         show(b);
         show(c);
         show(d);
         show(e);
         show(f);
         show(g);
         show(h);
         Base64 b64 = new Base64();
         show(b64.decode(b64.encode(a)));
         show(b64.decode(b64.encode(b)));
         show(b64.decode(b64.encode(c)));
         show(b64.decode(b64.encode(d)));
         show(b64.decode(b64.encode(e)));
         show(b64.decode(b64.encode(f)));
         show(b64.decode(b64.encode(g)));
         show(b64.decode(b64.encode(h)));
         b64.setLineLength(8);
         show((b64.encode(h)).getBytes());
*/
        }
    }// end main

    public static void test() {
        try {
            Base64 b64 = new Base64();

            //encode
            //str64 = b64.encode(str.getBytes());
            //System.out.println(str64);

            String str64 = "CwUEFYoAAAADjQMC7ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267ELJiY6w05267EI=";
            //decode
            byte[] theBytes = b64.decode(str64);
            show(theBytes);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
} // end Base64

